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Control of Apple Blue Mold by the Antagonistic Yeast Pichia anomala Strain K: Screening of UV Protectants for Preharvest Application

March 2011 , Volume 95 , Number  3
Pages  311 - 316

Rachid Lahlali, AAFC, Saskatoon Research Centre, 107 Science Place, Saskatoon, S7N 0X2, Saskatchewan, Canada, and Plant Pathology Unit, Gembloux Agro-Bio Tech, University of Liege, Passage de Deportes 2, 5030 Gembloux, Belgium; Yves Brostaux, Applied Statistics, Mathematics and Computer Science Unit, Gembloux Agro-Bio Tech, University of Liege; and M. Haissam Jijakli, Plant Pathology Unit, Gembloux Agro-Bio Tech, University of Liege

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Accepted for publication 28 October 2010.

When applied preharvest, antagonistic yeasts that act as biocontrol agents of postharvest fruit diseases must survive the environmental conditions in the field. In particular, UV-B radiation (280 to 320 nm) can greatly reduce their survival and effectiveness. The influence of artificial UV-B radiation on Pichia anomala strain K, an antagonistic yeast with potential for control of postharvest fruit diseases, was evaluated in vitro and in vivo. The in vitro 50 and 90% lethal dose values were 0.89 and 1.6 Kj/m2, respectively, whereas lethal values in vivo were 3.2 and 5.76 Kj/m2, respectively. UV protectants tested in combination with strain K included congo red, tryptophan, riboflavin, lignin, casein, gelatine, folic acid, tyrosine, and four mixtures. Riboflavin, folic acid, and the mixtures 1% folic acid + 0.5% tyrosine + 0.5% riboflavin (formula 2), 0.5% folic acid + 1% tyrosine + 0.5% riboflavin (formula 3), and 0.5% folic acid + 0.5% tyrosine + 1% riboflavin (formula 4) reduced yeast mortality caused by UV-B radiation in petri dish assays. Riboflavin, folic acid, gelatine, lignin, and tyrosine reduced yeast mortality caused by UV-B radiation on apple fruit surfaces. With the exception of lignin and folic acid, none of the compounds or mixtures increased significantly the ability of strain K to control the postharvest pathogen Penicillium expansum on wounded apple fruit. In contrast, casein, gelatine, tyrosine, congo red, riboflavin, and formulas 1 to 4 significantly reduced the effectiveness of strain K. Further investigations are justified to verify a potential benefit of lignin and folic acid for UV protection of strain K in preharvest applications.

© 2011 The American Phytopathological Society